在PDO中显示数据库的最后一个ID [重复]

Question

This question already has an answer here:

• PDO get the last ID inserted 3 answers

I am trying to get the last id number of Database. But It's showing only 0. I am learning PDO. Can anyone tell me how can I do it?

if($_SERVER['REQUEST_METHOD']=='POST'){
  $sql = "SELECT * FROM tablename";
  $stmt = $pdo->prepare($sql);
  $stmt->execute();
  $row = $stmt ->fetch();
  $showid = $pdo->lastInsertId();
  echo $showid;
}

</div>

Answer 1

lastInsertId will return the ID of a row that was inserted by the same connection. You can't use it outside of that context.

The easiest way to fetch the last ID would be to run something like,

SELECT max(id) FROM tablename

If you're using this in order to work out which ID should be inserted next, consider using an auto-increment column for your ID instead.